Health & Fitness

Accessory movements are the small gliding and sliding movements which occur inside a joint during normal movement but which cannot be performed in isolation by a person. They are essential to the function of a joint and if lost can interfere with the ability to perform movements or can contribute to painful conditions. In the hip the accessory movements are not obvious with few gliding and sliding movements due to its deep and stable nature. One accessory movement which does occur is upwards and downwards, i.e. compression into the socket and distraction of the femoral head out of the socket.

The cycles of compression and relaxation which occur with weight bearing and gait are essential to the health and nutrition of cartilage. As the cartilage is compressed it gives to some extent even though it is quite dense and once this is released it reverts to normal shape, squeezing the fluid out of it under pressure and then sucking it back in as force is removed. This sets up a pumping action of fluid up from within the cartilage and underlying bone, providing an essential fluid replacement mechanism to keep cartilage healthy.

The production of new cartilage is in response to the daily expected mechanical stresses put on a joint, and with the high forces involved in heel strike the cycle of stresses and relaxation are important to counter this. Encouraging larger movements in greater ranges may be useful to encourage growth of cartilage, however if loads are static or significantly reduced the opposite may occur. Loss of cartilage may occur with continued static loading, high bodyweight and allowing the joint forces to reduce by using a walking aid.

Resting a joint when it is painful is not a clearly positive strategy. Pain may be reduced when resting but the mechanisms which encourage regrowth of cartilage are not stimulated and the joint capsule may stiffen and reduce the available range of movement at the joint. This may increase the compressive forces in the joint and produce more pain. Whilst painful joints do need respect, in general arthritic joints are worse being still and better being kept moving about. The ability to achieve a rhythmical cycle of gait is very beneficial for the movements and the blood supply of the upper femoral structures.

The ligamentum teres, a band like structure running from the head of the femur to the socket, has blood vessels which may be affected by the cycle of gait which produces a effect of pumping fluid through. This may allow better blood supply to the head of the femur and keep the bone healthy. To maintain the density and normal composition of the bone in the upper femur it is important for this area to be subject to normal forces such as walking. Use of a walking aid or resting in bed can cause loss of bone density and mineralisation, with the bone becoming less flexible and less resistant to jars and strains.

Typically in western countries people utilise only a small part of the rather large range of movements available to the hip. Walking is a repetitive movement in only a small range and on sitting we don’t often go over ninety degrees flexion. As we get older we are less and less inclined to make our hips go to the ends of the ranges they are capable of. Hips seem to benefit particularly from keeping a variety in their movement available and stressing them to their extremes now and again. In eastern societies squatting, even to iron, is common, and our levels of hip arthritis may be higher than theirs.

A lack of use in the end ranges of a joint can mean the joint capsule will exhibit some tightening and in this way increase the compressive forces suffered by the head. Extension of the hip can be particularly affected by a difference in leg length. The longer leg in standing will tend to bend slightly at the hip and knee to keep the head level for the eyes to function best. This compensation can lead to stiffness developing with some loss of hip and knee extension as the hip develops a fixed flexion deformity.

Jonathan Blood Smyth is the Superintendent of Physiotherapy at an NHS hospital in the South-West of the UK. He writes articles about back pain, neck pain, and injury management. If you are looking for physiotherapist in Blackpool visit his website.